DE60206874T2 - A method and apparatus for providing a flow with minimal congestion of Ethernet traffic transmitted over the SDH / SONET network - Google Patents

Abstract

Disclosed is a method and device for handling Ethernet frame signals in a SDH/SONET network, the SDH/SONET network comprising network elements or nodes and fiber connections connecting the network elements, the method being characterized by the step of defining a new layer/network over the SDH/SONET network in order to manage the Ethernet signals over the SDH/SONET network, the new layer/network using the resources of SDH/SONET network in such a way as to optimize the provided services and the performances with reference to this specific type of transport. The step of defining a new layer/network comprises the steps of: defining at least two Ethernet Access Points, namely Ethernet interfaces at the SDH/SONET network boundary where the Ethernet signals can access/leave the SDH/SONET network; defining a Link as a pair of Ethernet Access Points providing a point-to-point connection; for any pair of Ethernet Access Points, defining corresponding Circuits, namely all the possible routes connecting the pair of Access Points through the SDH/SONET network; and dividing each Circuit into Pipes, namely a sequence of smaller segments. <IMAGE>

Description

The The present invention relates to the field of telecommunications and in particular the transmission from Ethernet frame over an SDH / SONET network. The present invention specifically relates to Method and apparatus for achieving a minimum delay in the transport Ethernet traffic frames over an SDH / SONET network.

As is known, is the data stream generated by an Ethernet device by nonuniformity namely, there is while periods with a more or less uniform transmission rate Ethernet packets and periods that take quite a long time Time passes between a received Ethernet frame and the next one. Such an unstable / nonuniform Traffic becomes common referred to as "burst" mode. In contrast, SDH or SONET traffic is constant Send / receive rate marked. In other words: every network element an SDH / SONET transmission network sends corresponding frames with a constant constant Rate. About that In addition, Ethernet frames do not have a fixed length / size but only a maximum Size of 1518 bytes).

It It is easy to see that these discrepancies are extremely difficult Interface technology for the two technologies with different conditions / characteristics leads.

A already available standing solution of the mentioned above Problems allows mapping from Ethernet frames to virtual ones SDH / SONET container as a transparent tributary; all incoming Bits become the output interface with a corresponding timing Information passed (frequency to regain the correct Bitrate on the receiver side). In the SDH / SONET payload also the dead times are between received Ethernet frames and the next mapped.

The general problem of transporting Ethernet frames over one SONET / SDH transmission network becomes current solved through a virtual SONET / SDH link. The transport of Ethernet Frame is performed according to the following main steps: the Bytes of a frame are applied to all available virtual containers it is going to be distributed the first frame byte maps to the first VC, the second frame byte in the second VC, etc .; due to the fact that virtual SDH / SONET container can take different paths the virtual containers should be realigned at the endpoint; and the bytes of the Ethernet frames are reoriented separated virtual containers and finally the frame is restored.

At present, if ethernet traffic over SDH / SONET networks are transported, some queues of Ethernet frame required. The Ethernet frames must have an SDH / SONET Network through point-to-point connections. Because a point-to-point connection through different routes, the the start and end points connect, can be represented, is a task, the best Route to find in terms of transport and network performance.

So far as the inventors know, there is no known solution This problem and the frames are over fixed point-to-point connections sent, independent of whether the for the resources provided for transport are overloaded and whether others Resources (which is a shorter Transit time enable could) are under-utilized.

The mentioned above Problem can even get worse if there is a mistake in the SDH / SONET virtual containers that carry the Ethernet frames. Currently Errors are made according to the relevant SDH / SONET recommendations treated, but in many cases introduces Error affecting a virtual container used for transport Ethernet frame is provided to a complete loss of traffic.

In US 2001/0043 603 A1 discloses an interface device and a method for directly adapting the Ethernet to the physical one Channel revealed. MAC frames are using LAPS in SDH / SONET Encapsulated SPE / VC. The LAPS encapsulation consists of the start flag sequence, the address field, the control field, the information field, FCS and the final flag episode. The device is used, for example, to an Ethernet interface for Telecom SDH / SONET transmission to disposal to deliver.

In the US 5,812,528 the measurement of roundtrip time in ATM virtual network connections is disclosed. The roundtrip time of cells is measured by inserting a time stamp into test cells in a first tester, transmitting those cells to a remote node in the network, looping the test cells from the remote node back to a source node, and determining their return time. The arrival timestamp and the departure timestamp are compared to determine the actual roundtrip time of the cell in the network. This information mation can be used to optimize network traffic flow, especially for existing virtual bit rate connections.

in the Regard to the above mentioned Main problem is the general object of the present invention, to overcome this effectively.

The The main object of the present invention is to provide a method and a facility available to be able to submit the route with the least delay for transmitting Frame from a starting point to an end point. The Characteristic of the transmission with the slightest delay turns out to be particularly advantageous when the network capacity is reduced is because one or more VCs are faulty.

A additional The object of the present invention is to provide a method implemented in hardware can be.

The The above and other objects of the present invention are achieved by a method according to claim 1 and a device solved according to claim 6. Further advantageous features of the present invention will be in appropriate dependent claims explained. All claims should be considered integral to the present description be considered.

The basic and general idea of the present solution is to assign the frame of the circuit that minimizes the transport delay carry out can.

Of the Link transmitter monitored constantly the Jam on each circuit and assigns every frame of the currently fastest Switch to, according to the last available traffic jam evaluation. The application of the least delay criterion leads to the best possible balance between all available standing circuits; the congestion on all these circuits should be more or less the same. The optimization of the circuit jams leads as well to optimize network congestion.

The present invention operates with a new layer / network layer placed over the SDH / SONET network to manage the transport of Ethernet traffic over the SDH / SONET network; this new layer / network layer uses the resources of the SDH / SONET network in such a way as to optimize the services and services provided with respect to this particular type of transport. This new layer has been fully described and described in an earlier patent application ( EP 02 290 445.2 ) of the same applicant. Its content is hereby incorporated by reference in its entirety.

The The present invention will be understood in Regard to the following detailed description, related with the phrase attached Drawings should be read, where

1 shows the structure of an exemplary virtual private network; and

2 highlights a connection with two associated circuits selected from the network of 1 ,

As mentioned above, the present invention operates in a layer / network layer acting as NETS (ie network for Ethernet transport over SDH / SONET) and is in EP 02 290 445.2 disclosed. The NETS includes basic elements listed below for a better understanding of the present invention.

The NETS model consists of five basic elements: access point, connection, circuit, pipe and path. An access point (AP) is an Ethernet interface at the boundary to an SDH / SONET network; it is the point where Ethernet traffic can enter or leave the SDH / SONET network. 1 shows a simple example of a network comprising five network elements (NE # 0 to NE # 4), where each network element has an access point: NE # 0 has AP # 0, NE # 1 has AP # 1, NE # 2 has AP # 2, NE # 3 has AP # 4 and finally NE # 4 has AP # 3. Of course, a network element can accommodate more than one access point. A pair of Ethernet access points defines a point-to-point connection; this connection is called Link. For example, defined with respect to 1 the pair AP # 0 & AP # 1 a link; the pair AP # 2 & AP # 4 defines another link, etc.

One SDH / SONET network could connecting two access points (i.e., building a link) over different ones Allow routes; every route is called a circuit. A circuit will obtained through the concatenation of pipes and could be considered as one Series connection of N pipes.

turn can connect any circuit / route that connects two access points a sequence of smaller segments are split; every segment is called a pipe.

The fundamental Pipeline is the virtual container that contains two network elements links; this is called path.

Regarding 1 there are two direct routes formed by 5 × VC-12 and 1 × VC-3, respectively, connecting AP # 0 and AP # 1; the first route is called Circuit A and the second Circuit B. Many more routes can connect the two access points, but for purposes of this example, two are enough.

2 highlights the selected link with the two corresponding circuits. The direction from NE # 0 to NE # 1 is considered first; Of course, the solution is applicable to both directions.

When Ethernet frames are received on AP # 0, they are stored in a queue of the LTX ₀ link transmitter of NE # 0.

Everyone Frame must be either circuit A (based on VC-12) or the Circuit B (based on VC-3) for the transport over the SDH / SONET network is assigned to the destination network element.

A frame assigned to a circuit is stored in the respective TX queue (CTX _A0 , CTX _B0 ), transported via the available virtual containers via the SDH network, stored in the RX queue CRX _A0 , CRX _B0 ) of the circuit and then forwarded to the connection receiver LRX ₁ .

2 does not show the SDH / SONET nodes (such as ADMs or XCs) of the network that do not map / decode Ethernet traffic into SDH virtual containers.

The basic and general idea of the proposed solution is assign the frame of the circuit that can carry the transport with the least delay.

The link transmitter LTX ₀ constantly monitors the congestion on each circuit and assigns each frame to the currently fastest circuit according to the last available congestion evaluation. The application of the least delay criterion leads to the best possible balance between all available circuits; the jam on all these circuits should be more or less the same. Optimizing the circuit jams also optimizes network congestion.

The measurement of the congestion of the circuit with the connection transmitter LTX ₀ , LTX ₁ , takes place in one direction only; the connection transmitter LTX _{0 of} the NE # 0 only needs to measure the congestion of the line A along the direction NE # 0-NE # 1. Similarly, the link transmitter LTX ₁ of NE # 1 has the task of measuring the congestion along the opposite direction, namely from NE # 1 to NE # 0.

Corresponding a preferred embodiment According to the present invention, a circuit transmitter becomes a delay mark Preferably, a delay marker is a bit that to transport along the circuit is using an ethernet frame the TX queue or a frame set up for it, if the TX queue should be empty.

The purpose of this bit is to measure the circuit delay, ie its jam along the direction from the link transmitter to the link receiver (eg from LTX ₀ to LRX ₁ ).

each Time if the link transmitter puts a delay marker on a circuit gives, a timer is started; if this timer is stopped, this gives a measure of the circuit delay. The timer stops when receiving the previously sent delay marker.

With even clearer reference to 2 Assume that the link transmitter LTX ₀ of NE # 0 gives the delay marker to the circuit A via CTX _A0 . The circuit A transports the delay marker to the destination. The delay line transport delay along circuit A (NE # 0 link transmitter LTX ₀ to NE # 1 link receiver LRX ₁ ) is the same as for an Ethernet frame because they are both stored in the same queue and transported along the same route.

As soon as the LRX ₁ link receiver of NE # 1 receives the delay marker of LTX ₀ , it provides an echo of that delay marker for the LTX ₁ link transmitter of NE # 1. Such an echo of the delay marker is transmitted back to NE # 0 along the opposite direction (from NE # 1 to NE # 0) using the same circuit A (and / or the circuit B, if available).

The task of this delay marker echo is to stop the timer of the link transmitter LTX ₀ to get an impression of the congestion on the circuit A.

The delay of the delay marker echo along the return path can not be avoided, but two conditions should be met to obtain more accurate information. Basically, the delay of the echo on the way back should be as short as possible; the shorter the echo delay, the more accurate the measurement. Furthermore, the return path delay for all scarf be the same; In this way, it influences the jam measurement for different circuits in the same way.

To satisfy both conditions, the echo of the delay marker in the reverse direction is transmitted as follows:
The delay marker has a higher priority than that for the queues of frames and skips any frames that may be stored. In this way the echo delay is reduced.

The echo will be on the way back over all available circuits (in 2 the circuits A and B) transmitted. The link transmitter stops the timer at the first reception of the echo, regardless of which return path has transmitted it; this further reduces the echo delay and should guarantee that the return delay is more or less the same regardless of the circuit being measured.

As already mentioned, the link transmitter stops the timer upon receipt of the first incoming call echoes; the value of the stopped timer represents a measure of the circuit delay.

possibly An average of the circuit delay is calculated by a Number of N of the last measurements of the delay is taken into account.

The Steps: Submission of a delay marker at the link transmitter; Transfer to the circuit transmitter; reception at the circuit receiver; Forwarding to the connection recipient; Returning a delay marker echo to the link transmitter that issued the delay marker; Calculation of the circuit delay; and calculating an average of the circuit delay ongoing for every circuit repeats.

• i. Ermitteln des Mittelwerts der Schaltungsverzögerung. Diese Verzögerung wird als Grundverzögerung angesehen, die nicht vermeidbar ist;
• ii. Berechnen (beim Verbindungssender) die Transportverzögerung des Rahmens entlang dieser Schaltung bei Nichtvorhandensein eines Staus. Diese Verzögerung wird benötigt, um den Rahmen entlang der Schaltung zu transportieren, wenn das Netzwerk unbelastet ist. Die Rahmenlänge (d.h. die Anzahl der Bytes) wird durch die Schaltungskapazität geteilt (d.h. Bytes pro Sekunde) und das Ergebnis ist die benötigte Verzögerung (in Sekunden). Wenn beispielsweise ein Rahmen von 256 Bytes betrachtet wird, ist die "unbelastete" Transportverzögerung der Schaltung A höher als die Verzögerung der Schaltung B, weil die Transportkapazität der letzteren mehr oder weniger fünf mal so hoch ist wie die Transportkapazität der Schaltung A (eine VC-3 im Vergleich zu 5 × VC-12).
• iii. Abschätzen des neuen zukünftigen Staus der Schaltung durch Addition des gegenwärtigen Stau-Mittelwerts zu der "unbelasteten" Transportverzögerung des Rahmens.
• iv. Wiederholen der Schritte i. bis iii. für jede zur Verfügung stehende Schaltung.
• v. Zuordnen des Rahmens an die Schaltung, die den kleinsten Schätzwert des künftigen Staus aufweist.

Therefore, if the link transmitter LTX _{0 has} a frame to assign to a circuit, it applies the criterion of the least delay according to the following steps:

• i. Determine the mean of the circuit delay. This delay is considered a basic delay which is unavoidable;
• ii. Calculate (at the link transmitter) the transport delay of the frame along this circuit in the absence of a jam. This delay is needed to transport the frame along the circuit when the network is unloaded. The frame length (ie the number of bytes) is divided by the circuit capacity (ie bytes per second) and the result is the required delay (in seconds). For example, if a frame of 256 bytes is considered, the "unloaded" transport delay of the circuit A is higher than the delay of the circuit B, because the transport capacity of the latter is more or less five times as high as the transport capacity of the circuit A (a VC). 3 compared to 5x VC-12).
• iii. Estimate the new future congestion of the circuit by adding the current congestion mean to the frame's "unloaded" transport delay.
• iv. Repeat steps i. to iii. for every available circuit.
• v. Assign the frame to the circuit that has the smallest estimate of the future congestion.

advantageously, The present invention does not apply the least delay criterion just considering of the present Traffic jams available at all standing circuits; but considered advantageously also, how are the present ones Change conditions would if the frame were assigned to this or another circuit.

Basically, the Access points AP # 0 and AP # 1 of the above example also via the circuit C representing the route NE # 0-NE # 3-Ne # 2-Ne # 1. The circuit C is different However, from the circuits A and B of at least two main reasons, namely by the presence of two intermediate nodes (NE # 3 and NE # 2) and through the circuit capacity.

Everyone Intermediate node brings with it a frame queue that the circuit delay elevated. It is clear that an intermediate node only applies the delay marker in Affects relationship to a greater delay, but the present invention can be applied without any problem.

The Circuit C is formed of the sequence VC-3 / VC-3/5 × VC-12; different types of virtual containers are used, and it is not clear what the capacity of the circuit is. It will a medium capacity just considered the circuit as a pipeline of a fixed section to look at, rather than as a series of pipelines with different sections; Nevertheless, again, the proposed solution is applicable.

Of the The main advantage of the present invention, as already mentioned, is that the best possible balance can be obtained between all circuits of a connection.

All Circuits should be more or less the same congestion / the same delay have bottlenecks avoid. This property also results in a limit the temporal displacement of the frames along different Circuits are transported.

The Network-level benefits become clearer when you consider that a virtual container of different circuits / connections in common can be used.

The VC-3, which connects NE # 3 and NE # 2, is part of a circuit C of compound AP # 0-AP # 1, but can also be used as a circuit for the connection AP # 4-AP # 2 be used.

One long jam along this virtual container represents a bottleneck for both Connections (and also for the network); the present invention avoids / limits these conditions by homogeneously distributing the traffic over the network resources.

The The result is an optimization of the bandwidth of the entire network. Thus, a new method and a new device has been shown and described, which fulfill the intended tasks and advantages. Many changes, Modifications, variations and other applications of the subject invention However, for the expert obviously after studying the description and the pendant Drawings disclosing preferred embodiments thereof

Claims (8)

Method for providing a data flow with minimal traffic jam for Ethernet traffic passing through a pipe from a transmission point (AP # 0) to a reception point (AP # 1) over at least an SDH / SONET network is routed, the at least one SDH / SONET network network elements or nodes (NE # 0, NE # 1, ... NE # 4) includes, fiber optic links connecting the network elements, and virtual SDH / SONET containers (VC-X #), with transmission over one new layer over the physical SDH / SONET network layer is managed and the new layer access points (AP #), connections between access point pairs and circuits, namely the possible ones Routes for comprising the connection of a pair of access points, the Method is characterized by: Generating a delay marker at the network element (NE # 0, NE # 1) of the transmission point (AP # 0, AP # 1); Transfer of the delay marker to the network element (NE # 1, NE # 0) of the receiving point (AP # 1, AP # 0) and back to the network element (NE # 0, NE # 1) of the transmission point (AP # 0, AP # 1) over at least a circuit; Calculate the time frame for the sending network element (NE # 0, NE # 1) for the return reception of the Delay marker; Determine the congestion of the circuit according to the time frame for the return reception of the delay marker; To calculate a mean value of the circuit jam under consideration a number of jams for the same circuit, Calculate a no-load transmission delay of a Circuit by dividing the number of frame bytes by the Circuit capacity, Estimate a new future Congestion of a circuit by adding the current mean value of the Circuit jams and load-free transmission delay, and Assignment of an Ethernet frame for transmission over the SDH / SONET network to the circuit with the smallest estimate for the new future Traffic jam. Method according to claim 1, characterized in that that all steps for all possible Circuits performed which are the transmission points and the reception points (AP # 0, AP # 1; AP # 1, AP # 0). A method according to claim 1 or 2, characterized in that the step of generating a delay marker at the transmitting network element (NE # 0, NE # 1) comprises the step of generating a delay marker at the transmitting station (LTX ₀ ; LTX ₁ ) of the transmitting network element and starting includes a timer. A method according to claim 3, characterized in that the step of transmitting a delay marker to the receiving network element (NE # 1, NE # 0) and back to the transmitting network element (NE # 0, NE # 1) via a circuit comprises the steps of generating a Delay marker echoes on the link receiver (LRX ₁ ; LRX ₀ ) of the receiving element network element, relaying to the receiving network element's LTX ₁ (LTX ₀ ), transmitting to the link receiver (LRX ₀ ; LRX ₁ ) at the transmit point and finally to the link receiver Link transmitter (LTX ₀ , LTX ₁ ) on the network element of the transmit point to stop the timer includes. A method according to claim 4, characterized in that the step of transmitting the delay marker echo to the link receiver (LRX ₀ ; LRX ₁ ) of the transmitting network element comprises sending the same delay marker echo over all available circuits and skipping all possible frame queues includes to reduce the delay of the echo as much as possible. An apparatus for transporting Ethernet frame signals in an SDH / SONET network, wherein the SDH / SONET network comprises network elements or nodes and fiber links connecting the network elements, the device comprising: at least one access point (AP # 0, AP # 1) for receiving / Outputting Ethernet frame signals; Means (LTX ₀ ; LTX ₁ ) for routing the received Ethernet frame signals to at least one connection, one connection comprising a pair of Ethernet access points establishing a point-to-point connection in the network; Means (CTX _A0 , CTX _B0 , CTX _A1 , CTX _B1 ) for transmitting frames to an available circuit, a circuit comprising one of the possible routes for the connection of a pair of access points through the network; and means for encapsulating the Ethernet frame signals in at least one virtual container for the selected available path, the device being characterized in that: said routing means (LTX ₀ ; LTX ₁ ) generate a delay marker which is connected to the receiving point (AP # 1, AP # 0) and back to the transmission point (AP # 0, AP # 1) via a circuit; Means for calculating the time frame for the transmission point (AP # 0, AP # 1) and the return reception of the delay marker are available; and means for determining the congestion of the circuit in accordance with the time frame for the return reception of the delay marker; and further means for calculating a mean value of the circuit jam taking into account a number of jam measurements for the same circuit, and means for calculating a load-free transmission delay of a circuit by dividing the number of frame bytes by the circuit capacitance, estimating a new future jam of a circuit by adding the current average of the circuit jam and load-free transmission delay, and assigning an Ethernet frame for transmission over the SDH / SONET network to the circuit with the smallest estimate for the new future jam. Apparatus according to claim 6, characterized in that said routing means (LTX ₀ ; LTX ₁ ) generating a delay marker further comprise a timer which is started when the delay flag is generated or transmitted. Device according to claim 7, characterized in that it further comprises connection receiver means (LRX ₁ ; LRX ₀ ) for generating a delay-marker echo for transmission to the connection transmitter (LTX ₁ ; LTX ₀ ) of the reception point which is connected to the connection receiver means (LRX ₀ ; LRX ₁ ) of the transmitting point, and finally the transmitting station (LTX ₀ ; LTX ₁ ) of the transmitting point to stop the timer.